"The List of Seven" by Mark Frost. W. Morrow, 1993.
This is an implausible novel built around the outline of Arthur Conan Doyle's life before Sherlock Holmes. In it, Doyle has written a book partially lifted from the writings of Madame Blavatsky and submitted it to a publisher. Unfortunately for Doyle, the plot mimics a real plot involving the publisher, zombies, spiritualism, and a tantalizing link to Nazism. Thinking Doyle is on the verge of exposing the plot, an elaborate trap is laid: he is invited to a seance where a murder takes place, and he is launched into a chain of sinister events which threaten his life and the succession of the British monarchy.